1. Field of the Invention
The present invention relates to a handy type image scanner and, particularly, to an improvement of a structure of a bottom portion of a body of a handy type image scanner employing a contact type image sensor.
2. Description of the Prior Art
The handy type image scanner, which is also called as a hand held printed matter scanning device, can pick up an image of an original as an image data for a personal computer by holding a body of the handy type image scanner by a hand of an operator and scanning the original by moving the scanner manually with respect to the original. The handy type image scanner is utilized as a peripheral device of a desk-top or notebook type personal computer. The handy type image scanner includes a contact type image sensor composed of a linear line of tightly arranged photo-electric conversion elements. An image of one full page of a thing such as an original, a photograph or a printed matter is read out by hand-holding the handy type image scanner, putting it on the page of the thing with the linear line of the tightly arranged photo-electric conversion elements of the contact type image sensor thereof being in a main scan direction and manually scanning the one page in a sub scan direction, while electrically scanning the photo-electric conversion elements in the main scan direction.
A conventional handy type image scanner of this type comprises, in addition to the contact type image sensor, rollers for allowing the handy type image scanner to smoothly scan along a surface of the original in the sub scan direction, a transmission unit ganged with the rollers to sense a relative moving distance of the image sensor with respect to the original and a casing, which houses all of the above mentioned components.
The transmission unit is constructed with, for example, a rotary encoder and a gear train for transmitting an amount of rotation of the roller to the encoder.
There are several types of construction of the contact type image sensor. In this description, however, one of them, which is disclosed in Japanese Patent Application Laid-open No. H6-291935, will be referred to as an example.
FIG. 1 is a schematic perspective view of the disclosed conventional contact type image sensor. In FIG. 1, a light emitting diode (LED) array 1 is a linear light source composed of, for example, a plurality of LED""s arranged in a linear line. Illumination light 5 emitted from the LED array 1 illuminates an original 4 and signal light 6, which is the illumination light 5 reflected from a surface of the original, is collimated by a rod lens array 3. The signal light 6 passed through the rod lens array 3 is collimated on surfaces of a plurality of optical sensor elements provided on an image sensor substrate 2 whose area size is the same as that of the original 4, to read an image of the original 4. The illumination light 5 emitted from the LED array 1 is featured by that it is incident on a surface of the original obliquely. Furthermore, although the image sensor is referred to as of the contact type, a space A is required between the surface of the original and a lower surface of the image sensor substrate 2 since the rod lens array is used. The space A is usually 10 mm to 20 mm.
FIG. 2 is a schematic perspective view of another example of the conventional contact type image sensor. In FIG. 2, illumination light 5 emitted from an LED array 1 illuminates a plurality of sensor elements 7 provided on a lower surface of an image sensor substrate 2. Each sensor element 7 is formed in a peripheral portion with a plurality of openings (not shown) for allowing the illumination light 5 to pass therethrough. The illumination light 5 passed through these openings formed in the peripheral portions of the sensor elements enters into optical fibers 12 provided in a fiber array plate 11 to illuminate an original 4. Signal light 6, which is the illumination light 5 reflected from the original 4, passes through the optical fibers 12 in a reverse direction to the sensor elements 7 to read the signal, respectively. A roller 10 functions to move the original 4 in a sub scan direction.
Although not shown, a plurality of switching elements for switching the respective optical sensor elements in order to scan the original 4 in a main scan direction by the optical sensor elements and output read-out signals of the respective optical sensor elements in time series, a drive circuit for driving these switching elements and a wiring therefor are provided on the image sensor substrate, in addition to the plurality of the optical sensor elements.
Now, an operation of the handy type image scanner will be described with reference to FIGS. 3A and 3B, in which FIG. 3A is a schematic functional cross section of the conventional handy type image scanner mounted with the conventional contact type image sensor shown in FIG. 1 and FIG. 3B is a bottom view of the handy type image scanner shown in FIG. 3A.
In this handy type image scanner, the contact type image sensor is provided within a housing 51 composed of a cover member 52 and a bottom plate 53. The roller 10 and a pair of rollers 50A and 50B are provided in the bottom plate 53 and the rod lens array 3 of the contact type image sensor is provided in the housing 51.
For a reading in a main scan direction in parallel to a horizontal direction in FIG. 3B, image signals in the form of photoelectric charge corresponding to luminous energy are read out sequentially from the respective optical sensors on a lower surface of the image sensor substrate 2 of the contact type image sensor. In reading the image signals, the illumination light 5 emitted from the LED array 1 passes through the bottom plate 53 to the original 4 and the signal light 6, which is the illumination light 5 reflected from the original 4, is collimated by the rod lens array 3, so that luminous energy of the signal light is read out by the optical sensor elements on the image sensor substrate 2.
For a reading in the sub scan direction in parallel to a vertical direction in FIG. 3B, the operator slides the handy type image scanner vertically on the original 4 with an aid of the rollers 10, 50A and 50B. In this case, the reading position of the handy type image scanner with respect to the original is detected by the rotary encoder ganged with the roller 10 through the gear train. Although three rollers are used in the shown case, the number of rollers is determined such that a distance between the original 4 and the image sensor substrate 2 is maintained constant and a smooth movement of the handy type image scanner with respect to the original is obtained.
This structure is featured by that it is necessary to provide a space between the rod lens array 3 constituting the contact type image sensor and the upper surface of the original since the illumination light 5 from the LED array is incident on the original obliquely and that a distance between the upper surface of the rod lens array 3 and the lower surface of the image sensor substrate 2 is made equal to the distance between the lower surface of the rod lens array 3 and the original by positioning the lower surface of the rod lens array 3 coplanar with or inside of the lower surface of the bottom plate 53. Furthermore, the housing 51 can slide smoothly on the surface of the original with the aide of the three rollers.
The reading in the main scan direction is performed in the same manner as that of the described contact type image sensor.
As to the reading in the sub scan direction, the operator manually slides the handy type image scanner vertically on the original 4 by utilizing the rollers. In this case, the reading position of the handy type image scanner with respect to the original is detected by the rotary encoder ganged with the roller 10 through the gear train, which is not shown.
In the case of the handy type image scanner shown in FIGS. 3A and 3B, the size of the housing 51 becomes large since the distance must be provided between the LED array 1 and the image sensor substrate 2 and the distance between the rod lens array 3 and the image sensor substrate 2 must be made equal to the distance between the rod lens array 3 and the original 4. Therefore, the merit of the portability of the handy type image scanner is degraded.
Furthermore, the rigidity of the housing is degraded, so that it tends to be warped. With warping of the housing, which may be caused in assembling it, and/or warping thereof caused by pressure applied thereto during a scanning operation, the rotation of the rollers 10, 50A and 50B may become irregular, resulting in vibration of the handy type image scanner hand held by an operator.
As mentioned, the size of the housing of the handy type image scanner, which uses the contact type image sensor shown in FIGS. 3A and 3B employing the rod lens array 3, is increased by the facts that the original 4 is illuminated with the oblique illumination light incident thereon and that the distance between the lower surface of the rod lens array 3 and the original is made equal to the distance between the upper surface of the rod lens array 3 and the lower surface of the image sensor substrate 2.
Contrary to the contact type image sensor shown in FIGS. 3A and 3B, in the contact type image sensor shown in FIG. 2, the lower surface of the optical fiber array plate (FAP) 11, which is the optical system for picking up the image, is coplanar with the upper surface of the original 4, which is substantially the same in vertical level as the peripheral surface of the roller 10, so that resolution of the picked-up image is improved. Furthermore, since it is possible to arrange the LED array 1 immediately above the sensor elements 7 and there is no need of providing a distance between the surface of the original 4 and the FAP 11, the size of the handy type image scanner may be reduced by applying the contact type image sensor shown in FIG. 2 thereto instead of the image sensor shown in FIGS. 3A and 3B.
In the case where the structure of the contact type image sensor shown in FIG. 2 is applied to the handy type image scanner as it is, however, the lower surface of the FAP 11 is made in direct contact with the upper surface of the original 4. Therefore, due to friction between the lower surface of the FAP 11 and the original, the scanning of the original by means of the scanner may become irregular, so that an image picked up thereby may be distorted.
Particularly, such phenomenon may become substantial for an original having an upper surface, which is not smooth but contains irregularity such as steps. Typical example may be a case where an image to be picked up by the scanner is a printed pattern of clothes, which are not completely flat.
The lower surface of the FAP 11, which becomes in contact with the upper surface of the original, is usually formed of glass material. However, since the glass surface is exposed externally, there may be a case where the glass is broken when an operator erroneously drops the handy type scanner.
Furthermore, the bottom plate of the handy type image scanner is usually formed by plastic molding, metal die casting or metal pressing. However, it is necessary to form through-holes in the bottom plate through which the rollers and the FAP are exposed externally.
In the case of the contact type image sensor using the FAP 11 shown in FIG. 2, the reduction of the size of the handy type image scanner is possible for the reason mentioned previously. However, in order to improve the resolution, the FAP 11 has to be in direct contact with the surface of the original. Therefore, the manual scanning operation may become irregular due to friction therebetween.
Furthermore, as mentioned above, the rigidity of the handy type image scanner is relatively low since the FAP 11 made of glass material protrudes externally, it may be broken relatively easily and, since the bottom plate of the handy type scanner has the through-holes in positions respectively corresponding to the rollers and the FAP 11. It may be possible to provide the rollers in a front and rear sides of the FAP 11 to thereby lift up the FAP 11 slightly, as shown in FIGS. 3A and 3B. In such case, however, the number of parts and the number of mounting steps thereof are increased disadvantageously.
An object of the present invention is to provide a compact and practical handy type image scanner, which allows a smooth manual scanning operation.
Another object of the present invention is to provide a handy type image scanner having an improved rigidity.
According to the first aspect of the present invention, a handy type image scanner having rollers in a bottom plate of a housing thereof has an optical fiber array plate (FAP), which extends along a rectangular opening portion of the bottom plate. An optical sensor for detecting signal light passed through the FAP is arranged within the housing. In order to prevent the FAP externally exposed in a lower surface of the bottom plate from contacting with an upper surface of an original to be scanned, a bank portion including a pair of parallel banks are formed on both longer sides of the rectangular opening portion of the bottom plate. The bank portion protrudes downward from the lower surface of the bottom plate. A downward protruding distance of a member such as the banks, the rollers and the FAP measured from a lower surface of the bottom plate will be referred to as xe2x80x9cheightxe2x80x9d, hereinafter. The heights of the banks and the rollers are determined such that at least a portion of the banks and the rollers can contact with the upper surface of the original simultaneously.
In such handy type image scanner, a cross section of each bank is a right-angled triangle and oblique sides of the right-angled triangle cross sections of the banks are located in positions remote from the FAP.
Alternatively, in the handy type image scanner mentioned above, the cross section of the bank may be a quarter round shape, an arc portion thereof being located in a remote side of the FAP.
In the present invention, the FAP protrudes downward from the lower surface of the bottom plate of the housing and a difference in height between the bank and the FAP, that is, a gap between the upper surface of the original and the lower surface of the FAP, is preferably set such that contrast transfer function (CTF) of the handy type image scanner becomes 30% or more.
Practical examples of the step are 0.1 mm or less for resolution of the optical sensor of 200 dpi and 0.045 mm or less for resolution of the optical sensor of 300 dpi.
When the bank portion includes a bank, which completely surrounds the rectangular opening portion, mechanical strength of the bottom plate can be improved. In the case where the bank portion includes a pair of banks, it is preferable that the height of portions of the banks, which extend in a main scan direction on the remote side of the rollers, is larger than the height of the rollers. In such case, it is possible that the height of the banks positioned between the rollers and the FAP is set equal to the height of the rollers. Alternatively, the height of the banks positioned between the rollers and the FAP is set equal to the height of the FAP measured from the lower surface of the bottom plate of the housing.
Furthermore, according to the second aspect of the present invention, a handy type image scanner comprises a housing having a bottom plate equipped with rollers protruded from a lower surface of the bottom plate, a rectangular opening portion provided in the bottom plate and extending along a rotation shaft of the rollers, a rectangular FAP extending in a major axis direction of the opening portion and protruding downward from the lower surface of the bottom plate toward a side of an original, an optical sensor provided above the FAP within the housing, for detecting signal light passed through the FAP and a bank portion downwardly protruding from the lower surface of the bottom plate, for preventing the FAP downwardly protruded from the lower surface of the bottom plate from contacting with a surface of the original, wherein the heights of the bank portion and the rollers are determined such that at least a portion of the bank portion and the rollers can simultaneously contact with the surface of the original and a step in height between the bank portion and the FAP is set to 0.1 mm or less.
In this handy type image scanner, the rotation shaft of the rollers may be supported by a lower side support member protruding downward from the lower surface of the bottom plate toward the side of the original.
Furthermore, the lowest end of the bank portion preferably has a pent roof portion covering a periphery of the FAP.
The bank portion may include banks provided along only both longer sides of the rectangular opening portion. When the bank portion further includes banks provided along both shorter sides of the opening portion, the heights of the banks along the shorter sides of the opening portion is preferably smaller than the height of the long banks provided along the longer sides of the rectangular opening portion in view of reduction of contact resistance between the FAP and the surface of the original. In the same view, the banks preferably include irregularity along the length thereof.
According to the third aspect of the present invention, a handy type image scanner for picking up an image of an original comprises an FAP for guiding signal light from the original, which is provided in a bottom plate of a housing of the scanner as an image read portion, wherein the FAP is protruded downward from the bottom plate by a predetermined distance, a bank portion having a tapered or a quarter round cross section and protruding downward from the bottom plate by a distance larger than the height of the FAP by 0.03 mm or less surrounds a periphery of the FAP and rollers, whose height measured from the bottom plate is equal to the height of the bank portion and contacts with the original, are arranged in parallel to the FAP as well as the bank portion.
According to the fourth aspect of the present invention, a handy type image scanner for picking up an image of an original comprises, as an image read portion in a bottom plate of a housing of the scanner, an FAP for guiding signal light obtained in a main scan direction of the original, an optical sensor provided above the FAP, for detecting the signal light guided by the FAP, a bank portion having a tapered or a quarter round cross section and protruding downward over the FAP by 0.03 mm or less, the bank portion being provided to substantially surround a periphery of the FAP protruded from the bottom plate and a roller provided in parallel to a lengthwise direction of the FAP, for detecting a position of the original in a main scan direction by a rotation angle thereof, wherein the heights of portions of the bank portion between the FAP and the roller measured from the bottom plate are made smaller than the heights of the other portions of the bank portion and the height of the roller is made substantially the same as the height of the FAP.